1. Field of the Invention
This invention relates to certain amorphous calcium compounds that are unique in their applications as remineralizers of caries lesions, cavities and root erosions of the tooth. These amorphous compounds when further containing a fluoride compound can also be used for topical fluoridation of the teeth. When used for either fluoridation or mineralization these compounds prevent further tooth decay and actually restore the lesions caused by dental caries.
2. Description of the Prior Art
When an incipient lesion or cavity develops on the surface of a tooth, the dentist traditionally fills the cavity that forms. This procedure may prevent the decay from spreading further, but does not restore the tooth to its original state. A considerable amount of research, however, has recently been directed toward the remineralization of dental lesions. The object of this remineralization has been the deposit of hydroxyapatite, Ca.sub.5 (PO.sub.4)OH, upon the surface of the tooth. Through this remineralization process further tooth decay is prevented and the tooth is restored to its original form.
In the area of remineralization of dental tissue there have been at least three approaches. One approach uses a metastable fluoride containing calcium phosphate solution supersaturated with respect to fluorapatite and hydroxyapatite which will form apatite slowly when applied. (The term apatite, as used in the present patent, includes not only pure apatite, but also apatite that includes other elements such as fluoride containing apatite.) A second method uses combinations of sparingly soluble calcium phosphates with crystallized tetracalcium phosphate and at least one different calcium phosphate in slurries or paste form. Such an approach is disclosed in U.S. Pat. No. 4,612,053 issued to Brown et al. Yet a third method uses potassium oxalate solutions to obturate the dental tubules.
These prior art methods are characterized by several practical problems. When a supersaturated solution using a single calcium phosphate is used, the remineralization process is extremely slow. The remineralization process is in fact so slow that an inconvenient amount of time is required for its completion. Another problem with the prior art methods is that as the apatite is deposited upon the teeth, the pH's of the treating solutions change. Such a change can make the solution either too acidic or too alkaline, creating the possibility of damaging the dental tissue.
Therefore, there remains a need for a treatment which achieves rapid remineralization of teeth similar to the natural process of biological mineralization, without the dissolution of the existing dental tissue.
In the area of topical fluoridation of the dental tissue there have also been at least three approaches. The first approach introduces simple fluoride containing compounds onto the surface of the dental enamel. This process relies upon the fluoride migrating through the enamel and strengthening the teeth. The second approach introduces acidulated phosphate fluoride, which involves the dissolution of some of the dental tissue and precipitation of calcium fluoride. The third approach involves an intermediate product of dicalcium phosphate dihydrate which is then converted to fluorapatite and precipitated upon the teeth. Each of these fluoridation methods is slow and inefficient and requires a long period of time in which to achieve adequate fluoridation of the dental tissue. There remains a need for a method in which fluoridation can be achieved rapidly and without damage to the teeth.
Although the prior art does not teach the use of amorphous calcium compounds for remineralization of teeth, it does refer to amorphous calcium phosphate as an aspect of the investigation of natural bone formation. See Synthetic Amorphous Calcium Phosphate and Its Relation to Bone Mineral Structure, Posner and Betts, ACCOUNTS OF CHEMICAL RESEARCH, Jan. 31, 1975; An Intermediate State in Hydrolysis of Amorphous Calcium Phosphate, Tung and Brown, CALCIFIED TISSUE INTERNATIONAL, 1983. This use, however, is significantly different from the present invention. Bone tissue is 50% organic material and 50% inorganic material, whereas dental tissue is 90% inorganic. As such, significantly different factors affect the treatment of the different tissues.
The prior art further teaches the use of amorphous tricalcium phosphate as surgical cement in teeth and bones. See U.S. Pat. No. 4,684,673 issued to Adachi. Contrary to the present invention, Adachi teaches a filler or a cement, not a composition which reconstructs the dental tissue.